1. Technical Field
The present invention is related to a synthetic peptide capable of inducing antibodies protective against human malarial infection caused by Plasmodium vivax sporozoites and the cloning of a gene encoding said peptide.
2. State of the Art
Of the four human malarias, Plasmodium vivax and P. falciparum are the most common and are a major cause of the malarial disease in the Tropics. Controlling these two infections would indeed improve health conditions in those regions of the globe where malarial infection still remains a major disease causing factor.
One approach has been the development of vaccines against the different stages in the parasite's life cycle. Sporozoites, the stage inoculated by mosquitoes to initiate the human infection, are covered with a particular protein known as the circumsporozoite (CS) protein. Antibodies to the CS protein have been shown to block infection in vivo (Potocnjak, et al., J. Exp. Med. 151:1504, 1980). Recently, the gene for the CS protein of P. falciparum was cloned, using anti-CS protein antibody screening of a mung bean nuclease digested genomic DNA library (Dame et al., Science 225:593, 1984) or of a cDNA library from sporozoite mRNA (Enea et al., Science 225:628, 1984). Recombinant (Young et al., Science 228:958, 1985) and synthetic peptide antigens (Ballou et al., Science 228:996, 1985; Zavala et al. Science 228:1437, 1985) of the repeat region in the middle of the CS protein of P. falciparum induce antibodies which block sporozoite invasion of liver cells in vitro.
The nature and function of the immunodominant epitope of the surface protein on sporozoites of the human malarial parasite Plasmodium vivax (P. vivax) has not heretofore been known.